This invention relates to techniques to generate sub-micron bubbles for example in use in treatment of contaminants in waste water frac-water and so forth, as well as other uses.
Waste water is a common form of water having contaminants. Waste water can arise in municipal waste as well as other types of waste, e.g., run off from farms, refineries, industrial processes, domestic applications, etc.
Frac-water on the other hand is principally associated with the oil and gas industry. The oil and gas industry has developed techniques to recover hydrocarbons such as oil and natural gas from shale deposits by so called “horizontal fracturing.” In horizontal fracturing, a stream of water is injected under pressure into wells disposed through shale deposits. Once fracturing is completed, the water (i.e., “frac-water”) is contaminated with petroleum residue and is returned to holding tanks for decontamination.
The underlying return water layer is contaminated, e.g., by high concentrations of alkanes, and may be somewhat saline. Generally, the underlying water contains from 1 to 10 parts per thousand chlorides (10,000-100,000 ppm) after usage. Other ranges are of course possible based on environmental conditions. Normally, drinking water standards generally require levels less than 250 ppm chloride, in order to have proper viscosity for discharge, whereas river discharge standards require generally levels less than 2,000 ppm, although this standard can vary.